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How to print single-colour logos and graphics on cardboard sheets for pizza boxes

Flexographic printing is a direct printing technique that uses a raised printing plate to transfer ink onto the surface of a substrate. It is used in numerous industrial applications, including the customisation of paper and cardboard packaging, bags, boxes and other materials intended for packaging purposes.

In the pizza box industry, printing can be used to reproduce logos, brand names, text and other graphic elements on cardboard sheets intended for box production. The process makes it possible to customise the packaging before subsequent converting operations, provided that the sheet format and substrate characteristics are compatible with the machine being used.

The Bag & Box 376 is a single-colour flatbed flexographic printer designed to print on the upper surface of boxes and flat bags. Its operating principle and printing unit configuration also make it worth considering for applications involving cardboard sheets intended for pizza boxes.

For this type of application, it is necessary to consider not only the printing area but also the sheet dimensions, the cardboard structure and the material feeding method.

How a flatbed flexographic printer works

In flexographic printing, the image to be reproduced is transferred onto the substrate using a printing plate, generally made of polymeric material. The raised areas of the plate receive the ink and transfer it to the surface to be printed through direct contact. The printing unit comprises several components that work together to distribute the ink and reproduce the image.

• Anilox roller: this is a cylinder with a micro-engraved surface, designed to meter and transfer a controlled amount of ink to the printing plate. The Bag & Box 376 is equipped with a ceramic anilox roller.
• Doctor blade: this component controls the amount of ink remaining on the anilox roller surface, helping to ensure controlled ink transfer during the printing process.
• Printing plate: This is the component that carries the artwork to be reproduced. It is made of polymer, with a thickness of 5.5 mm, and is mounted on the roller using double-sided adhesive tape with a thickness of 0.5 mm.
• Printing roller: this carries the printing plate and enables the image to be transferred to the substrate as it passes through the contact area.
• Ink supply system: the machine uses a tank with a pneumatic pump and continuous ink recirculation. The system supplies ink to the inking unit during operation.

Print quality depends on the interaction between these components, the correct preparation of the printing plate, the ink characteristics and the nature of the surface being printed.

The Bag & Box 376: construction and operating modes

The Bag & Box 376 is a flexographic printing machine designed for flat substrates. Its configuration includes a material handling system, a printing unit and a control panel for managing operations.

Cardboard sheets are fed manually, one piece at a time, and conveyed towards the printing unit by a belt. Pressure rollers help keep the material in the intended position as it advances.

The system is equipped with a photoelectric sensor to detect the presence of the cardboard. In automatic mode, substrate detection triggers the printing cycle. A manual mode is also available, allowing the operator to initiate printing on a single piece via the control panel.

This distinction is important for understanding how the production process is organised: automating the printing cycle does not mean that the sheets are fed fully automatically. The machine also allows the operating speed to be set and the graphic position relative to the cardboard to be adjusted. The configuration must be checked against the substrate characteristics and the required result.

Application to cardboard sheets for pizza boxes

Cardboard used to manufacture pizza boxes can be customised by printing single-colour graphic elements. Potential applications include reproducing company branding, logos, trade names, text and identification elements.

A single-colour flexographic printer allows the process to focus on a single colour separation. The artwork can be prepared using a dedicated printing plate, whose configuration determines the image transferred onto the substrate.

For pizza box cardboard sheets, the technical assessment must begin by distinguishing between flat, uncut sheets and die-cut blanks that have been laid flat. A flat sheet with a regular surface may present different feeding conditions from a pre-die-cut blank, where cuts, creases and shaped sections can affect stability during transport.

To determine compatibility with a specific pizza box format, the following factors must therefore be checked:

• Overall sheet dimensions;
• Width and position of the area to be printed;
• Cardboard thickness, rigidity and surface characteristics;
• Presence of die cuts, creases or other processing features;
• Required positioning accuracy for the artwork.

The ability to print a particular format cannot be determined solely from the stated maximum printing width. The substrate geometry and the conditions under which it is fed into and conveyed through the machine must also be taken into account.

Single-colour printing: characteristics and applications

Single-colour printing is used when the artwork can be reproduced using one ink colour. This configuration is suitable for a wide range of straightforward customisation applications in which legibility and the recognisability of graphic elements are the main objectives.

In pizza packaging, applications may include:

• Brand identification: printing a logo or trade name makes it possible to identify the manufacturer or brand associated with the packaging.
• Textual information: names, messages and other text elements can be reproduced using a printing plate produced according to the required artwork.
• Decorative elements: lines, symbols and other single-colour shapes can be incorporated into the graphic design to define the visual appearance of the cardboard.

The achievable print quality depends on the printing plate, the substrate characteristics and the correct adjustment of the printing unit. In particular, the cardboard surface, its flatness and any irregularities may affect the contact between the printing plate and the material.

Artwork management and job changeovers

One of the defining features of the flexographic process is the use of a dedicated printing plate for each design. When the required image changes, the corresponding printing plate must be prepared and mounted in accordance with the prescribed procedures.

Changing the artwork therefore involves preparation, positioning and print verification. The time required depends on the complexity of the image, the adjustment operations and the production conditions.

For sheets intended for pizza boxes customised for different customers, this workflow can be assessed in relation to the number of designs handled and the quantities required for each order.

Operational efficiency depends on the overall production process, including setup times, manual sheet handling and any operations required after printing.

Technical specifications of the Bag & Box 376

The main documented specifications of the F376-300 model are summarised in the following table.

The values in the table refer to the 376-300 model. When considering a specific machine version, the complete dimensional data, configuration and technical performance specifications should be verified.

The actual printing speed depends on the application and operating conditions. It does not necessarily correspond to the number of sheets processed per hour, since overall productivity also includes material feeding, setup and handling operations.

Inks and requirements for food packaging

Ink selection is an important consideration in packaging printing processes. The 376-300 uses water-based or solvent-based inks and features an ink supply system comprising a tank, a pneumatic pump and a continuous recirculation circuit.

When printing on sheets intended for pizza boxes, ink selection must take into account the type of cardboard, the surface being printed and the intended end use of the packaging.

Suitability for food packaging cannot be established solely on the basis of the printing technology or substrate material. The suitability of the materials used must be verified, and the potential for ink transfer must be assessed in relation to the intended use of the packaging.

When using water-based or solvent-based inks, the instructions provided in the relevant safety data sheets must be followed, along with the appropriate handling procedures and applicable installation requirements. Ventilation conditions must also be assessed, taking into account the risks associated with vapours and flammable substances.

Preliminary checks for printing pizza box cardboard

Before introducing a new cardboard format into the production process, it is advisable to carry out a technical assessment of the material and the printing conditions.

The assessment should include a trial using samples representative of the sheets actually used in production. This trial makes it possible to evaluate the cardboard’s behaviour during feeding, the positioning of the artwork and the uniformity of the printed result.

It is also useful to check the legibility of text and symbols, edge definition and print consistency on the material. For pre-die-cut cardboard blanks, particular attention should be paid to substrate geometry and the ability to convey the material correctly.

The results obtained make it possible to determine whether the format is compatible with the machine and identify any adjustments required for the application.

Frequently asked questions about flexographic printing on pizza box cardboard

What is a single-colour flexographic printer?

It is a machine that transfers an image onto a substrate using a raised printing plate and a flexographic inking system. The single-colour configuration allows monochrome graphics, such as logos, text and symbols, to be reproduced.

Can the Bag & Box 376 be used to print sheets intended for pizza boxes?

The machine is designed for single-colour printing on cardboard and for printing on the upper surface of boxes and flat bags. Its suitability for pizza box sheets must be verified based on the format, cardboard characteristics and feeding method.

Can pre-die-cut pizza box blanks be printed?

Compatibility with pre-die-cut cardboard blanks depends on the sheet geometry and material handling conditions. Cuts and creases may affect substrate transport and positioning. Testing with actual samples is therefore necessary.

What is the maximum printing width?

The documented maximum printing width for the F376-300 model is 300 mm. This figure refers to the printing width and should not be confused with the overall dimensions of the sheet that can be processed.

How is the cardboard fed into the machine?

Feeding is manual, with one piece introduced at a time. The material is conveyed using a conveyor belt and pressure rollers.

How is the printing cycle started?

The machine has an automatic mode, in which a photoelectric sensor detects the presence of the cardboard and triggers printing, and a manual mode, which allows the operator to initiate printing on a single piece.

Does flexographic printing also produce the finished pizza box?

No. The machine performs the printing operation only. Die-cutting, creasing, folding and assembly are carried out during subsequent cardboard converting stages.

Which factors affect the print result?

The main factors include printing plate quality and preparation, ink metering, cardboard surface characteristics and rigidity, sheet positioning and printing unit adjustments.

Even a simple pizza box can become a powerful communication tool. With flexographic printing, logos and graphics help make every package recognisable, turning cardboard into an extension of brand identity. The Bag & Box 376 opens up new customisation possibilities, to be explored based on substrate characteristics and the requirements of each application.

Written by Roberto Bortolotti – Senior Mechanical Engineer since 2001 | Team Giugni®